Method of producing photographic-process screens



H. EWALD April. 23, 1929. I

METHOD OF PRODUCING PHOTOGRAPHIC PROCESS SCREENS Original Filed Jan. 15, 1923 canvas which holds the colors on up bright and strong,

. for the natural Patented Apr. 23, 1929.

- UNITED STA HERMAN EWALD, or ciiicAGo, rumors.

METHQDOF rnonucme rnoroennrnicmnocnss seminars.

' Application filed January 15-, 1923,

My invention relates to a color separation process screen, and to a photographic process water-color sketches, machinery, or natural scenes and the like.

In a general way my invention contemplatesthe' reproduction of an original by the use of a screen provided with an irregularly wrinkled or corrugated coating.

The screen effect is accomplished by the texture which is high at the crest of the corrugation and deep between the corrugations, the deeper part between the corrugations having the effect of a dark portion of the screen and the higher part at the crest of the corrugation having the effect of a transparent portion. The effect of this screen on the negative is to give it an irregular open natural transparent effect, makes much more clearly and more like the original than would bGlPDSSlblG with the old half-tone screen. J

I also place the color directly in the surface of the screen, and :place the screen directly in front of the sensitized dry plate. My inven tion' contemplates particularly a close' contact illumination of the sensitized plate by a colored plate, which colored plate may also have a screen texture, although itis obvious that two separate plates may be employed, one being the color plate and the other the texture screen, or that a plate may be provided having a color screen on one texturescreen on the other. My method is so simple to use, that any photographer can easily get good results in color reproduction without much experience in handling the screen,

In reproducing an original in colors, all that is necessary to do is to use four of my screens of the proper color, making one negative from each screen, and then use these negatives without responding number of zinc etchings, from which the final reproduction is printed.

In printing the final reproduction, I use a flat coated material to receive the colors, such asmetal or specially prepared paper or top of the surface so that they do not sink flat but stand tion, for instance, of an oil painting, the effeet is strikingly similar to the oil painting itself, having the appearance of brush work reproduction of oil paintmgs,

plate the details stand outside and a any retouching to make a corso that in the reproduc- I SeriaLIil'o. 612,797. Renewed May 11, 1928.'

done by an artist in oil or water-color and pastel. a j

The' main inventive idea is in the color screen itself, and in the method by which it is reproduced. I

In the drawings- Fig. 1 is a greatly enlarged plan view of a fragment of the color screen, showing the wrinkled or corrugated coating; and Fig. 2 is a section on the line 22 of Fig. 1. In making my new screen, I use a glass 10 which is perfectly even on the surface, and coat the same with a specially prepared gelatine emulsion which is sensitized to light, when dried on the glass.

may be prepared as follows: 5 oz. of best hard clear gelatine are diluted in 10 oz. of distilled water at a temperature notover 120 degrees F. Two oz. of ammonia water is then added and the mixture is filtered three or four times through a felt filter. After this solution is' filtered it is poured warm onto a warm glass plate so that the solution can run easily all over the surface of the glass. This glass plate is then set in a dry oven with its coated surface level, and is dried at a temperature of about 90 degrees F for about 2 hours.

This dry coated plate'which is now sensitive to the light, is then exposed to a light (either to the sun or to artificial light) for a short time, as long as is necessary, depending upon the power of the light. This hardens the emulsion on the glass plate.

After the plate has. been exposed to the light for a certain time, as long as needed, it is -placed in a 25% acetic acid bath which causes the surface of the exposed emulsion to become This emulsion irregularly wrinkled or corrugated, the cor- 'rugations or wrinkles being discontinuous, and the surface having an appearance under a magnifying glass as though it were thickly sprinkled with small worms as indicated at 11. The plate may be exposed to the action of this .acetic acid bath for about 5 minutes, after which it is washed out for about an hour in running water. After it has been washed, it is cleared out in a bath of alum and citric acid, which makes the plate more transparent.

After the plate has thus been washed and cleared, it is placed in an acetic acid bath which is diluted with proper anilinedye colors which will soak into the emulsion coating on the glass plate, giving this coating the desired colon,

After the screen has thus been colored, it is dried in a dry room under a low temperature not over 80 degrees F. the drying being" best accomplished by cool air ventilation.

After the plate is thus colored and dyed, the emulsion screen surface is coated with a clear special transparent water-proof varnish which makes the emulsion coating more clear and transparent and water-proof, and keeps the colors in the gelatine surface protected from damp atmosphere which would make the screen filmy and destroy the clear transparent effect.

The use of the plate has been outlined above.

As previously stated, if the four color process is to be used, four of my screens of proper color are prepared, a negative is made from each screen, and these negatives are then used without retouching to make the corresponding number of zinc etchings from which the final reproduction is printed.

Having thus described my invention, what I claim as new and desire to secure by United States Letters Patent is: s

1. A method of, making a photographic process screen, comprising coating a glass plate with a smsitized gelatine composition which hardens on exposure to light, drying the coating, exposing the coating to the light to harden it and subjecting the coating to a 25% acetic acid bath, to cause the surface of the coating to become irregularly corrugated.

2. A method of making a photographic process screen, comprising coating a glass plate with a sensitize-d gelatine composition which hardens on: exposure to light, drying the coating, exposing the coating to the light to harden it and subjecting the coating to :1.

25% acetic acid bath for about minutes, to cause the surface of the coating to become in regularly corrugated. 3. A method of making a photographi process screen, comprising coating a glass plate with a composition of about 5 oz. of clear gelatine diluted with oz. of distilled water,

1 oz. of potassium b-ichromate and 2 oz. of ammonia water, drying the coating at a tem-- perature of about 90 degrees F. for about 2 hours, exposing the coating to light for a short time to harden it, subjecting the coating to a acetic acid bath to cause the surface of the coating to become irregularly corrugated, washing off the plate for about an hour in water, and subjecting the Washed plate to a bath of alum and citric acid to clear I it out and make more transparent.

4. A method of making a photographic process screen, comprising coating a glass in water, subjecting the washed plate to a bath of alum and citric acid to clear it out and make more transparent, and placing the washed and cleared out plate in anacetlc acid bath diluted with dye-color which will soak into the coating to give it the proper color.

In witness whereof, I have hereunto subscribed my name.

f HERMAN EWALD. 

